A well-known issue in monostatic continuous wave radar systems is the spillover signal, i.e., the direct leakage of the transmitted signal from a transmitter into a receiver. This unwanted spillover signal is picked up by the receiver and can drown the desired received signal, which represents the surveyed scene. The spillover signal can be especially problematic in integrated systems, where antennas need to be closely spaced to allow miniaturization, thereby increasing the spillover signal power. Recently, an on-chip spillover cancellation circuit has been implemented in a 79 GHz radar system-on-chip (see Davide Guermandi et al., A 79 GHz Binary Phase-Modulated Continuous-Wave Radar Transceiver with TX-to-RX Spillover Cancellation in 28 nm CMOS, 2015 IEEE INT'L SOLID-STATE CIRCUITS CONF. (Feb. 25, 2015)). The spillover cancellation circuit is able to filter out, in the baseband domain, the unwanted spillover signal. However, in order to improve functioning of the spillover cancellation circuit, the spillover signal power may need to be within a certain range, i.e., the power may need to be above a certain threshold.
For a simple radar system comprising only one transmit-receive pair, the transmitter subsystem and the receiver subsystem can be placed in such a way that the spillover signal power is above the required threshold at all times by calculating the interference pattern of the spillover signal. For radar systems comprising multiple transmit-receive pairs, each pair being fed with the same phase signal, the subsystem placement becomes more complicated but still feasible. However, for a MIMO radar system, in which the transmit-receive pairs are independently excited with a different phase, the problem of placing the subsystems to guarantee the required spillover signal power becomes very complicated. The main issue is that it is very difficult to calculate the numerous different possible interference patterns when taking into account the independently generated transmitted signals. As such, it becomes very complicated or even impossible to determine a location of the subsystems which would result in receiving a spillover signal power level above the certain threshold for each receiver subsystem in each of the possible interference patterns.